Wide-angle lens comprising eight components

ABSTRACT

A wide-angle lens comprises eight components and has a relative aperture of 1:5.6 and an angular field of at least 120*. The object side and the image side of a convergent central part of the lens are each faced by the concave sides of three divergent menisci.

United States Patent Inventors Eberhard Dietzsch Jena, District of Gera;Ernst Rumpoldin, Apolda, District of Erfurt, both of Germany App]. No.824,023 Filed May 6, 1969 Patented Jan. 11, 1972 Assignee Veb Carl ZeissJena Jena, Gera, Germany WIDE-ANGLE LENS COMPRISING EIGHT COMPONENTS 2Claims, 2 Drawing Figs.

US. Cl 350/214, 350/207 Int. Cl G02b 9/00, G02b 9/08 Field of Search350/207, 214, 215

References Cited UNITED STATES PATENTS 2/1956 Bertele 6/1962 Baker2/1968 Hudson 2/1956 Berteie FOREIGN PATENTS 1 1951 Italy 9/1960 GreatBritain 8/1966 U.S.S.R.

Primary ExaminerDavid Schonberg Assistant Examiner-Paul A. SacherAtt0rneyNolte & Nolte ABSTRACT: A wide-angle lens comprises eightcomponents and has a relative aperture of 1:56 and an angular field ofat least 120. The object side and the image side of a convergent centralpart of the lens are each faced by the concave sides of three divergentmenisci.

PATENTEU JAN] 1 I972 SHEET 1 OF 2 INVENTOR fi rama ably g,

ATTORNEY PATENTED JAN 1 1972 SHEET 2 OF 2 INVENTOR fi i @ef/mg ATTORNEWIDE-ANGLE LENS COMPRISING EIGHT COMPONENTS This invention relates towide-angle lenses comprising eight components and having a relativeaperture of 1:56 and an angular field of at least 120 and wherein theobject side and the image side of a convergent central part are eachfaced by the concave sides of three divergent menisci.

Lenses of the foregoing kind are preferably used in precision camerasfor aerial photogrammetry operating with highprecision shutters.

Known lenses of this or a similar type have the disadvantage that, ifthe space for the diaphragm is smaller than the 0.06 times the focallength, the-provision of a high-precision shutter is impossible. On theother hand, in the case where sufficient space is available an undesiredvignetting effect has to be tolerated when large angular fields areconcerned.

In wide-angle lenses having large angular fieldseven if dispersivemenisci enlarge the entrance pupil in conformity with the increase ofthe anglethe distribution of light in the image plane is mostunfavorable owing to the light decrease towards the margin. It isimperative, therefore, to obviate further deterioration due tovignetting.

A further disadvantage of such known lenses consists in incompletecorrection of the image errors in the margin of the image field. Inparticular, the sagittal image is not plane enough and the coma isgenerally bound up with considerably asymmetry errors deleterious to thequality of the image.

The present invention aims at obviating the foregoing disadvantages byproviding a wide-angle lens in which the space for the diaphragm isgreater than 0.06 times the entire focal length and which at arelatively aperture of 1:5.6 defines an image angle of at least 120without vignetting, and in which the correction for astigmatism isdecisively improved and substantial coma correction free from asymmetryerrors is obtained in the entire image field.

To this end, the present invention consists of a eight-componentwide-angle lens of the foregoing kind, characterized in that theconvergent central part of the lenses comprises two convergent elementsthe less curved of which enclose a diaphragm and the stronger curvedfaces of which are each conjugate to a comparatively thick dispersivemeniscus, that each of these two menisci has at least one convergentconvex cemented face conjugate to the diaphragm and lies at a distancetherefrom which is less than 0.015 times the entire focal length so asto provide an air space in the form of a thin convergent meniscus, andthat the distance between the convex exterior faces of the twoconvergent elements of the central part is smaller than 0.35 times theentire focal length. The less curved faces of these two convergentelements thus include a diaphragm space large enough for a shutter.

Accordingly, and contrary to the known practice, the convergent cementedfaces for the correction of the astigmatism and coma of such lenses arenot located in the convergent central part, but are included in the twomenisci symmetrically enclosing that part. These two menisci, which arenaturally rather thick and may only be spaced the necessary shortdistance away from the central part, are also instrumental in thecorrection of the spherical aberration. The air spaces in the form ofthin convergent menisci between the convergent central part and the twoadjacent thick menisci enable the correction of the coma errors, whichare particularly great in such lenses. Not only does a construction ofthe foregoing kind substantially flatten the astigmatic images and theasymmetry error but offers the additional advantage of favorable comacorrection throughout the entire image field, provided that the radiusdifference of each of the said image field, provided that the radiusdifference of each of the said two meniscus-shaped air spaces is lessthan 0.025 and that the radii of these air spaces are within 0.22 and0.33 times of the entire focal length.

The reduction of the comatic asymmetry error is accompanied by zone-freecorrection of the distortion if the radius of the outer convex surfaceof the thick meniscus directly on the image side of the convergentcentral part is numerically at least 1.1 times greater than the radiusof the outer convex surface of the thick meniscus directly on the objectside of the convergent central part and if, at the same time, thearithmetical mean of the refractive index of the element nearest theimage and that of the element adjacent thereto is greater than 1.6.

Apart from the correction of the monochromatic image errors, importanceattaches also to good chromatic correction, which, as is well known,poses some difiiculty in the case of so large an image field. Inparticular, to keep the chromatic zonal aberration of the distortion andthe chromatic coma errors within narrow limits, it is advantageous toprovide that the Abbe number of the element last but one on the imageside of the convergent central part is smaller than 45 and that thethick meniscus directly on the image side of the convergent central parthas a further cemented surface near the cemented surface convex towardsthe diaphragm, the radius of this further cemented surface beingnumerically at least three times greater than the entire focal length,and that the refractive indices of the elements contacting each other inthis further cemented surface differ by less than 0.03, the Abbe numbersof these latter elements differing from each other by at least eightunits in such a manner that the element of the greater Abbe number lieson the image side of the said further cemented surface.

The useful spectral range can be increased by providing that themeniscus directly on the object side of the convergent central part hasalso a further chromatically active cemented surface which is concavetowards the diaphragm.

In order that the invention may be more readily understood, reference ismade to the following Tables I and II and the accompanying drawing whichillustrates diagrammatically and by way of example two constructionalexamples of the invention. Table 1 corresponds to FIG. 1 of the drawing.Table 11 corresponds to FIG. 2 of the drawing.

TABLE 1 Focal length f=l; relative aperture 1:5.6; angular field 121;diaphragm space l =0.0618 1 Thicknesses and Refractive Abbe numbersRadii distances indices n,, u

d,=0.06828 1.51633 64.0 r +0.6l 125 d =0.01869 1.60562 43.9 rad-0.27184d,=0.l2722 1.55115 49.6 r =+28.73676 diaphragm space r =+4.87763 d=0.0l869 1.61293 37-0 r =+0.56805 d =0.05247 1.72825 28.3 rap-0.70771TABLE [1 Focal length f=l; relative aperture 125.6; angular field 121;diaphragm space l..=0.06209 Focal length f==l; relative aperture 1:5.6;angular field 121; diaphragm space [P006181 Thickncsses and RefractiveAbbe numbers Radii distances indices n v d,=0.06828 1.51633 64.0 rF+O.6l125 1,=o.2s924 r -,='+0.52622 2. Wide-angle lens comprising eightcomponents and having a relative aperture of 1:5.6, an angular field ofat least and a diaphragm space l =0.06209, the characteristics of saidlens being as follows:

Focal length #1; relative aperture 156; angular field 121; diaphragmspace l =0.062O9

1. A wide-angle lens comprising eight components and having a relativeaperture of 1:5.6, an angular field of at least 120*, and a diaphragmspace l4 0.06181, the characteristics of said lens being as follows:Focal length f 1; relative aperture 1:5.6; angular field 121*; diaphragmspace l4 0.06181 Thicknesses and Refractive Abbe numbers Radii distancesindices nd Nu r1 +1.29775 d1 0.06828 1.51633 64.0 r2 +0.61125 l1 0.21736r3 +0.89057 d2 0.05678 1.51633 64.0 r4 +0.43467 l2 0.28924 r5 +0.52622d3 0.31583 1.67786 55.5 r6 -0.63863 d4 0.01869 1.60562 43.9 r7 +0.27184l3 0.00489 r8 +0.28280 d5 0.12722 1.55115 49.6 r9 +28.73676 l4 0.06181diaphragm space r10 +4.87763 d6 0.12794 1.55361 51.4 r11 -0.29168 l50.00331 r12 -0.28280 d7 0.01869 1.61293 37.0 r13 +0.56805 d8 0.152381.66446 35.9 r14 -5.11339 d9 0.11788 1.67786 55.5 r15 -0.62426 l60.27429 r16 -0.44284 d10 0.05247 1.72825 28.3 r17 -0.70771 l7 0.20744r18 -0.53779 d11 0.06397 1.58913 61.2 r19 0.90718
 2. Wide-angle lenscomprising eight components and having a relative aperture of 1:5.6, anangular field of at least 120*, and a diaphragm space l4 0.06209, thecharacteristics of said lens being as follows: Focal length f 1;relative aperture 1:5.6; angular field 121*; diaphragm space l4 0.06209Thicknesses and Refractive Abbe numbers Radii distances indices nd Nur''1 +1.40773 d1 0.06773 1.52088 60.2 r''2 +0.64601 l1 0.15506 r''3+0.80930 d2 0.05644 1.61272 58.6 r''4 +0.44316 l2 0.30661 r''5 +0.53348d3 0.11958 1.66680 33.1 r''6 +1.16220 d4 0.22175 1.66755 41.9 r''7-0.58504 d5 0.01693 1.61659 36.6 r''8 +0.26232 l3 0.00815 r''9 +0.27680d6 0.12996 1.55232 63.5 r''10 -7.50150 l4 0.06209 diaphragm space r''11+9.08195 d7 0.13175 1.56384 60.7 r''12 -0.29219 l5 0.00264 r''13-0.28565 d8 0.01693 1.58215 42.0 r''14 +0.57550 d9 0.13957 1.65128 38.3r''15 +25.53558 d10 0.12504 1.64328 47.8 r''16 -0.66308 l6 0.28465 r''17-0.43336 d11 0.05193 1.72342 38.0 r''18 -0.65051 l7 0.19993 r''19-0.52868 d12 0.06435 1.52944 51.8 r''20 -1.08893